How to Install a Dimmer Switch

Control the ambience of a room with a new dimmer switch.

hand on dimmer switch

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Project Overview
  • Working Time: 20 minutes
  • Total Time: 30 minutes
  • Skill Level: Intermediate
  • Estimated Cost: $10 to $30

A dimmer switch is a type of light switch used to control the brightness of a connected light fixture. This is accomplished by regulating the flow of electricity to the light fixtures with a dimmer control, such as a dial or slider. You can use a dimmer switch to choose the best light level for the room at any time of day and even reduce the amount of electricity you're using.

Installing a dimmer switch isn't a difficult task if you have experience working with home electrical systems. For those that have never worked on the electrical infrastructure of the home, this job can be a good way to learn how to safely upgrade and maintain your electrical system. Find out how to install a dimmer switch with this informative guide.

Choosing a Compatible Dimmer Switch

Before learning how to install a dimmer switch, it's necessary to purchase a dimmer switch to replace the existing light switch. Not all dimmer switches can be used with every type of lightbulb, so it's important to check the product information provided by the manufacturer to find a dimmer switch that is suitable for the an incandescent light bulb, LED light bulbs, or CFL bulbs.

Another factor to check before purchasing a dimmer switch is whether you need a single pole or three pole dimmer switch. A single pole dimmer switch is used when the existing light switch is the only control for the current light fixture. You can use a three pole dimmer switch if there are currently two existing switches that control a single light fixture.

New advanced dimmer switches with smart features may also require a neutral connection to function. Not every home has neutral wiring, so if you are investing in a high-tech dimmer, it's important to check if the dimmer switch requires neutral wiring and if your home has neutral wiring before proceeding. This can be seen by pulling out the existing light switch without disconnecting it. If the home has neutral wiring, you should see a white wire inside the junction box.

Safety Considerations

Whenever working with electricity, it's important to take proper precautions to avoid accidental electrocution. Make sure to turn off the electricity to the light switch before starting this project. Use a non-contact voltage tester to verify that the electricity is off before touching the wires. Additionally, it's recommended to wear electrical insulated gloves while you work to ensure that if there is a live current, you are protected against electrocution. If you are not confident in your abilities, it's best to call in an electrician rather than risk a potentially fatal accident.

Additionally, when you are working on the light switch, check to ensure that the junction box is large enough for the new dimmer switch. If the box is too small or there are too many wires jammed into it, then the heat produced by the electrical connection will not be able to properly dissipate. This could lead to dangerous overheating, short-circuiting, and fire. Avoid this issue by upgrading to a larger junction box before installing the new dimmer switch.

What You'll Need

Equipment / Tools

  • Screwdriver
  • Non-contact voltage tester
  • Wire cutters
  • Wire strippers
  • Needle-nose pliers


  • Wire labels
  • Dimmer switch


How to Install a Dimmer Switch

Follow these straightforward directions to learn how to replace an existing light switch with a new dimmer switch.

  1. Turn Off the Power

    Before starting the project, head to your fuse box or breaker panel to turn off the breaker switch that controls the flow of electricity to the target light switch. If you have a fuse box, you will need to remove the fuse that is connected to the target light switch.

  2. Remove Faceplate and Test Current

    Use a screwdriver to remove the faceplate from the existing light switch, but do not proceed until you have confirmed that the electricity to the switch is off. You can check the flow of electricity with a non-contact voltage tester. Test the black wires in the junction box to confirm that the electricity to the switch is turned off. If there are multiple switches in the same box, make sure to test all of them.

  3. Label Wires

    Once you are certain the electricity is off to the switch, use a screwdriver to loosen the mounting screws at the top and bottom of the existing light switch. Gently pull the switch out of the junction box without removing the wires. Use wire labels to mark the wires currently attached to the switch.

    • Black/Red Wire: The load wire is typically black, but in some cases it may be red. This wire extends from one terminal on the existing switch to the light fixture.
    • Black Wire: The line wire is always black. This wire connects to the main electrical box, extending to a terminal on the existing switch. If you aren't certain which wire is the line wire, keep the light switch off, but turn the breaker switch back on. With the electricity restored to the light switch, use the non-contact voltage tester to check both black wires. The wire with voltage is the line wire. The black wire without voltage is the load wire.
    • Green or Copper Wire: The ground wire will generally have a green sheath. In some situation, the ground wire may be bare copper. This wire extends from the junction box to the designated terminal on the light switch.
    • White Wire: Not every home has a neutral wire, but if you home does, then make sure to purchase a dimmer switch that is compatible with neutral wiring. This wire is used with advanced electronic dimmers, so be sure to check the manufacturer's directions to determine if the dimmer switch requires a neutral connection. Neutral wires connect to three different points: the light fixture, junction box, and existing switch.
  4. Disconnect Wires

    Use a screwdriver to loosen the mounting screws that are currently holding the wires in place on the existing light switch. If the ends of the wires are damaged, consider snipping the tip of the wire and using wire strippers to peel back about 3/4-inch of the plastic sheathing to expose new wiring for the connection.

  5. Connect Dimmer Switch

    If your dimmer switch requires a neutral connection, then connect the neutral (white) wire on the switch to the neutral wire from the wall. This should end up be a three-way connection point, linking the light fixture, junction box, and the dimmer switch. If the dimmer switch does not need a neutral connection, proceed directly to wiring the line wire.

    Connect the black line wire to the terminal on the back or side of the dimmer switch. Next, connect the black or red load wire to the terminal on the back or side of the dimmer switch. Finally, connect the green or copper ground wire to the dimmer switch terminal.

    Use needle-nose pliers to help bend the wires around the terminal screws on the dimmer switch, then tighten the screws with a screwdriver to secure each wire to the new dimmer switch.

  6. Slide Dimmer Switch Into Position

    Neatly push the wires back into the box, ensuring there is enough space for the dimmer switch. With the wires in the box and out of the way, slide the dimmer switch into the junction box and secure it with screws at the top and bottom of the switch. Put the faceplate over the dimmer switch and tighten the screws on the faceplate.

  7. Turn On Electricity and Test the Switch

    When you are satisfied that the job has been completed properly, head back to the fuse box or breaker panel. Reinstall the fuse or flip the switch on the breaker panel to turn on the electricity to the switch. Turn the switch on to check if the new connection is correct and adjust the dimmer control to ensure the dimmer switch works properly.

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